1. Field of the Invention
This invention relates generally to microstrip Y-junction circulators, and particularly to a circulator providing transitioning between circuit elements on different substrates.
2. Description of the Prior Art
Circulators have multiple ports which provide signal transmission from one port to an adjacent port while decoupling the signal from the other ports. Y-junction circulators have three ports. Circulators are used in many electronic systems for selectively directing a signal to various circuit elements. For example, they are used in radar systems as duplexers to couple the transmitter and receiver to a single radar antenna. They are also used in many other applications such as signal generator protection circuits, and transmitter injection locking circuits as an example. The use of planar geometry circuitry in conjunction with microstrip transmission lines in the millimeter wave frequency applications has resulted in reductions in size and weight of the circuit elements. An example of a planar geometry microstrip circulator is found in U.S. Pat. No. 4,749,966 entitled "Millimeter Wave Microstrip Circulator" issuing Jun. 7, 1988 to Stern et al, the inventors of the present invention, which is herein incorporated by reference. With the increasing use and number of components fabricated with the planar type geometry, the cost of manufacturing and assembly have been reduced, as well as the physical size of the resulting package of circuit elements. However, there is a continuing need to further decrease the number of circuit elements and the physical size of the circuit elements. Additionally, the planar geometry of the microstrip circuit elements has resulted in difficulties of packaging and transitioning of the circuit elements to provide a compact package. Therefore, there is a need to improve the packaging and assembly of microstrip circuit elements.